90 Questions
Which of the following colors on a DNA microarray indicates that a gene is not expressed?
Black
Which of the following is NOT a type of regulatory protein that binds to DNA?
Homeodomains
What type of regulation occurs when an activator protein binds to DNA to stimulate transcription?
Positive regulation
What type of regulation occurs when a repressor protein binds to DNA to prevent transcription?
Negative regulation
What is the function of transcriptional regulators?
To control the expression of thousands of different genes
Which of the following structural polypeptide domains is found in most transcription regulators?
All of the above
In bacterial gene expression, what happens if the concentration of tryptophan is low?
The genes needed to make tryptophan are expressed
In eukaryotic gene activation, how do activator proteins bind to the transcription complex?
Indirectly via mediators
What type of regulation occurs when histone modifying enzymes and chromatin-remodeling complexes are recruited to the promoter region?
Acetylation
What does the intensity of red or green binding to a spot on a DNA microarray indicate?
The number of mRNAs expressed
Which of the following statements is true about gene expression in human cells?
Gene expression in human cells can be controlled at many steps from DNA to protein.
What is the most common control point for gene expression in eukaryotic cells?
Transcriptional control
Which of the following is true about differentiated cells?
Differentiated cells can change the genes they express without altering the DNA sequence.
How do scientists determine which genes are expressed in certain conditions?
By identifying all the RNAs produced by the cells.
What does a DNA chip (microarray) contain?
Many dots, each dot containing a different gene.
What does the intensity of red or green binding to a spot on a DNA chip indicate?
The number of mRNAs expressed by the gene.
What does a yellow spot on a DNA chip indicate?
The gene is expressed in both conditions being compared.
What do blank spots on a DNA chip indicate?
The gene is not expressed.
How do yeast cells change the genes they express in response to different carbon sources?
By altering the transcription of their genes.
What genes do yeast cells express when grown in glucose and ethanol conditions?
Yeast cells express genes for both glucose and ethanol utilization.
Which of the following is a mechanism for regulating eukaryotic gene expression after transcription?
Alternative splicing
What is the function of histone acetyltransferases in chromatin remodeling?
They add acetyl groups to histone tails, leading to nucleosome opening and transcription activation
What is the role of microRNAs in gene expression regulation?
They inhibit mRNA translation and promote mRNA degradation
What is the function of the iron regulatory protein (IRP) in mRNA translation regulation?
It binds to the iron-response element (IRE) and blocks ribosome binding in low iron conditions
Which of the following is NOT a control mechanism for eukaryotic gene expression?
Chromatin remodeling
What is the function of ubiquitin in protein degradation?
It attaches to a protein to mark it for destruction
What is the role of activator proteins in gene expression regulation?
They enhance transcription by binding to regulatory sequences of genes
What is the function of the RNA-induced silencing complex (RISC) in gene expression regulation?
It guides microRNAs to target mRNAs for inhibition and degradation
What is the effect of adding acetyl groups to histone tails in chromatin remodeling?
It reduces the positive charge, leading to nucleosome opening and transcription activation
How do microRNAs regulate gene expression?
They inhibit mRNA translation and promote mRNA degradation
Which of the following is true about the energetic cost of translation in cells?
1 ATP is used during aminoacyl-tRNA activation
What is the relationship between genes and proteins?
Genes encode proteins
What is gene expression?
Genes contain information to make RNA
What is the function of mRNA in the process of gene expression?
mRNA allows the cell to separate information storage from information utilization
What is the role of RNA in gene expression?
RNA allows the cell to separate information storage from information utilization
What is the function of activator proteins in gene expression regulation?
Activator proteins bind to DNA to stimulate transcription
Which of the following is true about the genetic code and translation?
There are 64 possible mRNA codons
What is the reason for the redundancy in the genetic code?
There are more codons than amino acids
What is the role of tRNA in translation?
To carry amino acids to the ribosome
What is the function of aminoacyl-tRNA synthetase?
To covalently link amino acids to the correct tRNA
What is the role of the initiation factors in protein synthesis?
To bind the small ribosome subunit to mRNA
What are the three steps of translation?
Initiation, Elongation, Termination
Which of the following molecules is responsible for structural support and catalyzing amino acid covalent linkage?
Ribosomal RNAs (rRNA)
What is the approximate composition of a ribosome?
2/3 rRNA and 1/3 protein
What is the function of small nucleolar RNAs (snoRNAs) in the processing of pre-rRNA?
Help process pre-rRNA
What is the most abundant type of RNA in cells?
Ribosomal RNAs (rRNA)
What is the function of transfer RNAs (tRNA)?
Carry amino acids to the ribosome during translation
What is the function of messenger RNAs (mRNA)?
Contain a continuous sequence of nucleotides encoding a particular polypeptide
Which of the following is true about termination in mRNA translation?
Termination occurs when a stop codon is recognized by a release factor.
What can cause early termination in translation?
All of the above
What is the process of selective destruction of mRNA with premature termination codons called?
Nonsense-mediated decay
What remains on mRNA when premature termination occurs?
Exon-junction complex
How do some antibiotics work in relation to translation?
They inhibit the binding of tRNAs to the A site
What does the presence of polyribosomes indicate?
The presence of multiple ribosomes on a single mRNA
Which of the following is true about transcription in eukaryotic cells?
Transcription in eukaryotic cells involves three distinct RNA polymerases.
What is the role of transcription factors in transcription?
Transcription factors help RNA polymerase recognize the promoter.
Which of the following is a difference between DNA replication and transcription?
DNA replication requires a primer, while transcription does not.
What is the function of small nuclear RNAs (snRNAs) in eukaryotic cells?
SnRNAs help process messenger RNAs (mRNAs).
Which of the following is true about gene expression in eukaryotic cells?
Only the non-template strand of DNA is used to make RNA molecules.
What is the function of microRNAs (miRNAs) in gene expression regulation?
MiRNAs help regulate gene expression.
Which molecule is required for the initiation step of translation?
GTP
What is the energetic cost of translation in cells?
1 ATP and 1 GTP
What is the function of mRNA in gene expression?
To translate RNA into protein
What is the role of microRNAs in gene expression regulation?
To bind to mRNA and prevent translation
What is the approximate composition of a ribosome?
RNA and proteins
What is the role of the iron regulatory protein (IRP) in mRNA translation regulation?
To inhibit translation of mRNA
Which of the following is true about ribosomes in cells?
Ribosomes consist of both rRNAs and proteins
What is the function of snoRNAs in the processing of pre-rRNA?
SnoRNAs help process pre-rRNA
Which type of RNA is most abundant in cells?
rRNA
What is the approximate composition of a prokaryotic ribosome?
2/3 rRNA and 1/3 protein
What is the function of the C-terminal domain (CTD) of a RNAP-II subunit?
The CTD is responsible for transcription initiation
What is the role of spliceosomes in mRNA splicing?
Spliceosomes remove introns from pre-mRNA
Which of the following is NOT a type of RNA synthesized during transcription in eukaryotic cells?
Small nuclear RNA (snRNA)
Which of the following is true about the template strand during transcription?
It is the non-coding strand of DNA
What is the function of transcription factors in transcription?
To help RNA polymerase recognize the promoter
Which of the following is a difference between DNA replication and transcription?
DNA replication requires a primer, while transcription does not
Which of the following is true about gene expression in eukaryotic cells?
Transfer RNAs (tRNA) are synthesized by RNA polymerase I
What is the function of small nucleolar RNAs (snoRNAs) in eukaryotic cells?
To process ribosomal RNAs (rRNA)
Which of the following is true about the genetic code?
There are 64 possible mRNA codons.
What is the reason for the redundancy in the genetic code?
To increase the efficiency of protein synthesis.
What is the role of tRNAs in translation?
To deliver amino acids to the ribosomes during protein synthesis.
What is the function of aminoacyl-tRNA synthetase?
To covalently link amino acids to their corresponding tRNAs.
What is the function of eIF2 in protein synthesis initiation?
To recognize and bind to specific mRNA codons.
What is the function of eEF2 in protein synthesis elongation?
To facilitate the movement of the ribosome along the mRNA during translation.
Which of the following is true about termination in mRNA translation?
Termination is mediated by the binding of release factors to the mRNA.
What can cause early termination in translation?
All of the above
What is the function of the exon-junction complex (EJC) in mRNA translation?
The EJC helps in the selective destruction of mRNA with premature termination codons.
What does the presence of polyribosomes indicate?
Polyribosomes indicate that multiple ribosomes are simultaneously translating the same mRNA molecule.
How do some antibiotics work in translation?
Some antibiotics inhibit the binding of release factors to the mRNA.
What is the role of nonsense-mediated decay in mRNA regulation?
Nonsense-mediated decay helps in the selective destruction of mRNA with premature termination codons.
Study Notes
DNA Microarray and Gene Expression
- Green color on a DNA microarray indicates that a gene is expressed, while red color indicates that it is not expressed.
- A yellow spot on a DNA microarray indicates that the gene is equally expressed in both samples.
Transcriptional Regulation
- Activator proteins bind to DNA to stimulate transcription, resulting in positive regulation.
- Repressor proteins bind to DNA to prevent transcription, resulting in negative regulation.
- Transcriptional regulators are proteins that bind to DNA to control gene expression.
- Most transcription regulators have a structural polypeptide domain called a DNA-binding domain.
Bacterial Gene Expression
- When the concentration of tryptophan is low, the operon is turned on, allowing the expression of genes necessary for tryptophan synthesis.
Eukaryotic Gene Expression
- Activator proteins bind to the transcription complex, stimulating transcription.
- Histone modifying enzymes and chromatin-remodeling complexes are recruited to the promoter region, allowing gene expression.
- The most common control point for gene expression in eukaryotic cells is transcriptional regulation.
Gene Expression Regulation
- MicroRNAs (miRNAs) regulate gene expression by binding to messenger RNA (mRNA) and preventing its translation.
- The iron regulatory protein (IRP) regulates mRNA translation by binding to iron response elements (IREs) in mRNA.
Translation Regulation
- RNA-induced silencing complex (RISC) regulates gene expression by degrading mRNA.
- Ubiquitin is involved in protein degradation, which can regulate gene expression.
Ribosome and Translation
- Ribosomes are composed of 60% RNA and 40% protein.
- The three steps of translation are initiation, elongation, and termination.
- Aminoacyl-tRNA synthetase is involved in the initiation step of translation.
- Transfer RNAs (tRNAs) bring amino acids to the ribosome during translation.
- Messenger RNAs (mRNAs) carry genetic information from DNA to the ribosome.
Gene Expression in Eukaryotic Cells
- Gene expression is the process of creating a functional product from a gene, such as a protein or RNA.
- Gene expression is regulated at multiple levels, including transcription, translation, and post-translational modification.
- Small nuclear RNAs (snRNAs) are involved in the processing of pre-mRNA.
- MicroRNAs (miRNAs) regulate gene expression by binding to mRNA and preventing its translation.
- The iron regulatory protein (IRP) regulates mRNA translation by binding to IREs in mRNA.
Test your knowledge on the control of gene expression in eukaryotic cells. Explore how cells regulate gene expression, from DNA to RNA to protein. Learn about the different mechanisms and steps involved in controlling gene expression.
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